we shouldn't have the external pressures or junk science or make believe experts coming in to affect our jury. >> reporter: saturday the judge barred prosecution experts from testifying saying they failed to use generally accepted scientific techniques in claiming zimmerman's voice is not the one screaming. >> do you think he's yelling help? >> yes. >> what is -- >> there's gunshots. >> you just heard gunshots? >> yes. >> how many? >> just one. >> reporter: zimmerman has pleaded not guilty to second-degree murder saying he fired in self-defense. >> the prosecutors losing this critical ruling, they're going to have to rely even more on the testimony of the young woman who spoke to trayvon martin by cell in the final minutes of his life. >> reporter: the case sparked protest and rekindled the uneasy conversation about race. a discussion focused on recent days on the all women jury of six who will decide his fate. trayvon martin's parents say they want justice for their son. >> the concept of equal justice under the law isn't a black or white value, it's an american value. >> reporter: